Short flame travel combustion chamber design



Jan. 11, 1955 'MQ FF SHORT FLAME TRAVEL COMBUSTION CHAMBER DESIGN Filed May 22, 1952 M Attorneys United States Patent SHORT FLAME TRAVEL COMBUSTION CHAMBER DESIGN Archie D. McDuflie, Berkley, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Deiaware Application May 22, 1952, Serial No. 289,251

3 Claims. (Cl. 123191) This invention relates to combustion chambers for engines and has particular relation to combustion chambers capable of operation at relatively high compression ratios on commercial grades of hydrocarbon fuels.

It is proposed to form an engine combustion chamber in such a way that a relatively large part of the combustion chamber will be formed within a compactly designed firing chamber or space where the first part of the charge to burn is ignited. It is then proposed to form the remaining parts of the combustion chamber to provide a plurality of outwardly extending spaces or chambers where the burning of the charge will terminate. By providing a plurality of places where the burning of the charge may terminate, the charge is in effect divided into a plurality of parts in which the final burning of the charge occurs at lower temperatures and pressures.

In combustion chambers formed in this manner it has been found that the burning of the entire charge is completed in a shorter time and it is therefore possible to increase the compression ratio to a greater extent than would be possible in combustion chambers heretofore constructed.

In the drawing:

Figure 1 is a fragmentary cross sectional view of an engine, taken partly in a plane through the cylinder axis and the spark plug of the engine and partly in a plane through the axis of one of the valves of the engine.

Figure 2 is a fragmentary bottom plan view of the engine head employed in the structure disclosed by Figure 1. Figure 2 is taken in the plane of line 2-2 on Figure 1 looking in the direction of the arrows thereon.

The engine illustrated by the two figures of the drawing, comprises a cylinder block 11 having one or more cylinders 12 formed therein. The block 11 also has cooling liquid cavities 13 formed therein and adapted to receive cooling fluid for cooling the walls of the cylinders 12. The cylinders 12 have reciprocal pistons 14 adapted to be secured to the connecting rods of the engine crankshaft by piston pins indicated at 16. The cylinders 12 are closed at the outer ends by a cylinder head 17 which may be bolted to the block 11 upon a cylinder gasket indicated at 18. The end walls 19 and 21 of the pistons 14 and block 11 respectively and the opposed but adjacent wall 22 of the head 17 may be formed in any suitable manner and at any angle with respect to the axes of the cylinders 12, although for the purpose of illustration these walls are shown to have adjacent plane surfaces disposed in spaced relation to one another by the gasket 18 and extend normally with respect to the axes of the cylinders.

The head 17 also is formed in such a way as to provide cooling liquid cavities 23 and through which cooling fluid may be circulated for the purpose of cooling the wall 22 and other parts of the head 17. The wall 22 has inlet and exhaust openings or ports formed therein which are adapted to be closed by inlet and exhaust valves indicated at 24 and 26 respectively. The inner surfaces of the valves 24 and 26 may form substantially a continuation of the lower plane surface of the wall 22 of the head 17. The valves 24 and 26 are adapted to close inlet and exhaust passages such as that indicated at 27 which are formed in the head 17 through the jacketed space 23. The stems for the valves 24 and 26 are slidably mounted in the head 17 in bushings indicated at 28 and are adapted to be actuated in any suitable manner for admitting explosive charges to and exhausting prod- 2,699,160 Patented Jan. 11, 1955 nets of combustion from the cylinders 12 in timed relation to the operation of the pistons 14.

The shallow space of uniform depth between the plane surface of the wall 22 of the head 17 and the adjacent wall 21 of block 11 and wall 19 of piston 14 is formed in such a way as to provide a minimum mechanical clearance space or quench area 29 which forms a part of the combustion chamber 31 of the engine 10. The combustion chamber 31 also comprises a cavity, chamber or part 32 formed in the end wall 19 of the piston 14 and a cavity, chamber or a part 33 formed in the lower wall 22 of the head 17. Additional spaces forming part of the combustion chamber 31 are the annular clearance spaces 34 and 36 formed in the lower surface of the wall 22 around the valves 24 and 26. The valves 24 and 26 are positioned in the head 17 at one side of the cylinder 12 and the cavity 33 is formed in the head 17 at one side of and somewhat between the valves 24 and 26 and on a diameter of the cylinder 12 normally intersecting a line between the axes of the valves 24 and 26. The cavity 32 is formed in the wall 19 of the piston 14 at one side of the axis of the cylinder 12 and overlaps parts of the valves 24 and 26 and a part of the cavity 33. The cavity 32 may be of any desired shape but as shown is compactly formed substantially by a hemispherical surface projecting into the plane surface of the wall 19 of the piston 14. The cavity 33 may also be of any desired shape but as shown is of compact formation with the outlet therefrom being of substantially circular formation. The cavity 33 extends into the head a considerable distance so as to provide a relatively large space partly overlapping the cavity 32 in the piston 14 and having an end extending away from the cavity 32 like the end of the cavity 32 which overlaps the valves 24 and 26. A spark plug 37 is secured in the head 17 with the ignition terminals 38 thereof disposed within the combustion chamber 31 directly opposite the overlapping parts of the cavities 32 and 33.

When ignited by a spark across the terminals 38 the charge in the combustion chamber 31 will burn rapidly across the overlapping parts of the cavities 32 and 33. There will be a final burning of the part of the charge in the end of the chamber 33 which does not overlap the cavity 32. Since the largest part of the space forming the combustion chamber 31 is formed by the cavities 32 and 33, and since the remote end of the cavity 33 is relatively near the terminals 38 and the spark plug 37, this final burning of the charge within the cavity 33 will take place in such a short time that a relatively high compression ratio and fuel having a relatively low octane rating can be used without detonation occurring in the remote end of the chamber 33. The charge must burn across the relatively compact space forming the overlapping parts of the cavities 32 and 33 before it starts to burn in the end of the cavity 32 which overlaps the valves 24 and 26. The last part of the charge to burn therefore may be in the quench space 29. Since the ratio between the wall area and the volume of the quench space 29 is relatively large it is apparent that there will not be an excessive rise in the temperature and pressure of the last to burn part of the charge within the quench area 29. The parts of the clearance spaces 34 and 36 which extend around the valves 24 and 26 and which are non-exposed to the flame in the cavity 32 will also burn relatively slowly and without excessive increases in temperature and pressure due to the small cross section area of these clearance spaces.

It will be apparent therefore that the charge has been divided into a number of parts which either burn too quickly for detonation to occur or the final parts of which burn in spaces where the flame front is cooled and the acceleration of which is opposed by the relatively high ratio between the wall surface and the volume of the space containing the final part of the charge to burn. It will also be noted that the depth of the cavity 33 decreases as it approaches the quench area 29. The resultant decrease in the depth of the flame front as it approaches the quench space 29 will tend to prevent roughness in the engine by decreasing the rate of burning as it approaches the last part of the charge to burn.

I claim:

1. An engine comprising a cylinder having a reciprocal piston therein, said piston and the head of said cylinder having uniformly spaced and oppositely disposed and generally plane and adjacent wall surfaces forming a minimum clearance space between said piston and the head of said cylinder, inlet and exhaust valves in the head of said cylinder and forming substantially a continuation of said plane wall surface of said head and overlapping a part of said plane wall surface of said piston, said head being also formed at one side of said valves to provide a cavity projecting therein from said plane wall surface of said head, said piston being also formed to provide an other cavity projecting into said piston from said plane wall surface of said piston, said cavity in said piston having a part overlapping parts of said valves and a part overlapping a part of said cavity in said head, and a spark plug having the ignition terminal end thereof projecting into one of said cavities in substantially the middle of a wall of said cavity in directly opposed relation to the overlapping parts of said cavities.

2. An engine comprising a cylinder having a reciprocal piston therein, said piston and the head of said cylinder having uniformly spaced and oppositely disposed and generally plane and adjacent wall surfaces forming a minimum clearance space between said piston and said head of said cylinder, inlet and exhaust valves in said head of said cylinder and having inner Wall surfaces forming substantially a continuation of said plane wall surface of said head and overlapping parts of said plane wall surface of said piston, said piston being formed to provide a cavity extending into said piston for said plane wall surface of said piston and overlapping the remaining parts of said inner wall surfaces of said valves and extending between said valves and across said piston and terminating adjacent the opposite side of said piston, said head being formed at one side of and between said valves to provide another cavity extending therein from said plane wall surface of said head and overlapping the end of said cavity in said piston remote from said valves and extending beyond the end of said cavity in said piston and away from said valves and overlapping said plane end wall surface of said piston beyond said cavity in said piston, and a spark plug having the ignition terminal end thereof projecting into one of said cavities and in directly opposed relation to the overlapping part of the other of said cavities said overlapping parts of said cavities in which said ignition terminal end of said spark plug projects being constructed to provide a greater part of volume of said cavities than the outwardly projecting end of either of said cavities.

3. An engine as defined by claim 2 and in which said cavity extending into said piston from said plane wall surface of said piston is a hemispherical cavity.

References Cited in the file of this patent UNITED STATES PATENTS 1,943,495 Thomas Jan. 16, 1934 2,146,032 Scott Feb. 7, 1939 2,204,068 Chapman June 11, 1940 FOREIGN PATENTS 429,378 Great Britain May 29, 1935 433,342 Great Britain Aug. 13, 1935 604,997 Great Britain July 14, 1948 791,894 France Dec. 18, 1935 

